This invention relates to the field of horseshoes, and more particularly to the high-performance, light-weight aluminum alloy shoes for race horses, known as racing plates.
It is necessary to provide a race horse with plates that are best suited to the conditions of the track. A trainer will change the configuration of the plates to improve the speed of a horse, just as the tires and suspension of a racing car are changed to enhance performance on the track. Therefore each horse is fitted by a "plater" (farrier) with racing plates (light-weight aluminum alloy horesehoes) to match the individual running mechanics of that specific horse to a normal running surface. If the running surface changes, that match is disturbed. Therefore as rain softens a track's consistency, it is typical for a large number of horses to be lined up at the plater's shop to have their shoes changed before racing. Then when the track dries out those same horses come back to again have their plates replaced to suit the harder surface.
Each major race track also has specifications on racing plate configurations, particularly those tracks with grass surfaces. The shoes are specified by the track stewards, and controlled by a horse shos inspector. Therefore moving a horse from one track to another may require a change of shoes, and a change from the track to the grass will certainly require a shoe change; as calks of any kind are often prohibited on grass courses. The ability to optimize the traction of the horse's hoof on each track surface by correct selection and orientation of calks may be a significant factor in winning races. Examination of hoof prints shows that every horse shoe slide along the track surface a measurable amount on every stride. As the hoof strikes the track it skids forward slightly, just as the tires of a landing jet aircraft skid and smoke until they accelerate to match the speed of the landing surface. In turns the horse's hoof tends to slide sideways slightly due to centrifugal force, in much the same manner as the tires of a race car slide outwards in a turn. In addition, as the driving hoof reaches the end of the stride it loses traction and slides backwards, flipping dirt into the air behind it, much like an accelerating knobby motorcycle tire in the dirt. Since each of the four horse shoes sequentially hits the track approximately 200 times per mile, this gives the horse at least 800 individual skids along the surface. Optimizing traction and reducing the skidding in a stride by as little as five one-thousandths of an inch (the thickness of one horse hair) can change the distance covered by 4 inches in a mile, a far greater distance that the losing margin of many races. The weight of the components of a horse shoe is also critical. Every gram attached to a horse's foot accelerates from zero to over 80 miles per hour (more than twice the nearly 40 MPH speed of the horse's body) and back to zero in every stride. Each shoe is picked up as dead weight from one hoof-print on the track, lifted about 12 inches off the ground, thrust forward approximately 26 feet and pounded down to form the next hoof-print. Again, a race horse does this weightlifting exercise more than 800 times per mile, and every extra gram is a drain on the total strength and energy that the horse can contribute to the race. That is why modern racing plates are made of light-weight aluminum alloy.
A racing plate is attached to a horse's hoof with tapered nails that are driven through a row of rectangular holes in the plate, the holes being aligned within an elongated groove or channel extending substantially around the U-shaped plate and having sufficient depth in which to recess the nail heads. The nails are driven into the hoof at an angle, whereby the point of the nails emerge from the outer hoof surface and are bent over to secure them.
The specialized aluminum-alloy racing plates usually have some pattern of steel calks that are either cast or swaged in place to engage the track surface like the cleats on an athlete's shoes. Such calks are of several types including the "toe grab", an arcuate blade around the front of the shoe; "jar calks", a short transverse blade just forward of the heel areas; "stickers", long blades parallel to the side of the shoes; and "heel blocks" that may provide elevation and traction at the heels of the shoes. Although presently-used racing plates normally have all the calks cast in place, additional traction, particulary in turns and turning maneuvers on soft running surfaces, may be added. This is done by adding steel "sticker" calks between the toe and heel for lateral friction. The added steel calks have rectangular shanks that are pounded into some of the nail holes of the plate. This is a rather crude process, and the resulting security of attachment is not reliable. Other than such added stickers, it is generally impractical to add or remove calks. Therefore the plates must removed and replaced to alter the traction. In order to change a plate, the bent-over nail points must be straightened and clipped off, and then the nails pulled to release the plate. Once the plate is removed, the new plate must be similarly installed by driving in and crimping over new nails. The farrier usually shift the new shoe to try to avoid the old nail holes, sometimes resulting in mis-aligned shoes that degrade the horse's stride. Every removal and installation damages the horse's hoof to some degree, as each nail is a source of potential damage to the hoof or foot. Frequent plate changes, which are required to optimize the horse's performance as weather and track conditions change, increases the probability that a horse may be injured.
Proir to the development of the present invention there was no practical method for changing th calk pattern without replacing the plates. Replaceable calks have been known for draft horses for many years. These fall into two general types, calks that thread directly into tapped holes in the horseshoe, such as taught by Meissner (Austria 41759) and Fairchild (Britain 210,942). These patent are simply threadably-attachable calks that have no means for orientation on the shoe. Other prior art inventions employ systems of attachable calks that use conventional machine screws for attachment, such as shown by Bowers (U.S. Pat. No. 1,315,080) and Slater (U.S. Pat. No. 1,390,171). The present invention relates to both types of screw-attached calks. The principal shortcoming of these prior-art systems is that they are all very heavy and complex, and provide for only toe and heel traction areas. They were designed for draft horses with heavy shoes, pulling in a straight line, with little regard for weight or racing conditions.
A primary purpose of the present invention is to provide a reconfigurable racing plate system in which various calks for track adaptation, wear and stride correction may be screw attached in any of several orientations in a number of locations, to provide absolute minimum weight calks that are easily attached, re-oriented or removed, and to provide calks that may be quickly and easily attached to presently available racing plate without removal of the plates from the horse's hoofs.